This invention relates generally to advances in medical systems and procedures for prolonging and improving human life. More particularly, this invention relates to an improved method and system for alleviating urinary obstruction caused by enlargement of the prostate by performing thermal high frequency ablation for urethral enlargement.
A majority of all males over 60 years old experience partial or complete urinary obstruction because of the enlargement of the prostate. This condition usually originates from benign prostatic hyperplasia (BPH), which is an increase in cell mass near the urethra, or less likely, from prostate cancer. Both of these conditions involve an increase in prostatic tissue mass, which in its increased state encroaches on the urethra and obstructs the urinary pathway.
In the case where urinary obstruction is caused by BPH, a common treatment involves a medical procedure using a side-cutting instrument and/or endoscope to surgically enlarge a passageway for urine flow through the prostate. The side-cutting instrument, which is typically passed through an endoscopic tube, is passed through the penis into the urethra and is used to surgically remove prostate tissue and part of the urethra at the point of the obstruction. This procedure is referred to as xe2x80x9cTrans-urethral Resection of the Prostatexe2x80x9d (or xe2x80x9cTURPxe2x80x9d). Typically, the TURP procedure removes more than superficial tissue layers, that is, more than a diameter of 10 millimeters around the urethra, since the BPH condition could advance, creating repeated BPH obstruction. Using the TURP procedure, the surgical cavity that is created in the prostate can be tailored to the prostate size, both in length and diameter. The TURP procedure can also avoid critical structures such as the bladder neck, the rectal wall, which is adjacent to the prostate, and the erectile nerves at the border the prostate on the rectal side.
In the case where urinary obstruction results from prostate cancer, surgical prostatectomies are commonly used to eliminate the obstruction.
In recent years, less invasive systems and procedure that inflict less trauma on the patients have been attempted. One such procedure, called xe2x80x9cTrans-urethral Needle Ablationxe2x80x9d (or xe2x80x9cTUNAxe2x80x9d), involves passing a radio-frequency (RF) instrument such as a catheter, cannula, sheath, or scope into the urethra. The RF instrument houses special RF electrode tips that emerge from the side of the instrument. The tips are pushed out of the instrument along off-axis paths to pierce the urethral wall and pass into the prostatic tissue outside of the urethra. The TUNA system and procedure attempts to leave the urethra intact and uninjured by the application of RF heating.
Another minimally invasive technique for treating BPH is Trans-urethral Microwave Thermo Therapy (or xe2x80x9cTUMTxe2x80x9d). This involves use of a cooled catheter which also delivers heat energy to the prostate. A catheter that has a microwave probe inside of it is inserted into the urethra to the point of the prostate. The microwave probe is typically a microwave antenna which is located inside the catheter near its distal end and is connected to an external generator of microwave power outside the patient""s body. In this way the prostate is heated by radiative electromagnetic heating. At the same time the catheter is cooled by circulation of a coolant fluid within the catheter. The objective is to cool the urethra and thereby to prevent damage to it by the heating process which is occurring in the prostatic tissue that is outside of and at a distance from the urethra. Thus, the TUMT procedure seeks to preserve the urethra and the prostatic tissue immediately outside of the urethra by cooling the catheter with fluid coolant that is circulated within the catheter. In the TUMT procedure, the prostatic tissue immediately around the urethra and the urethra itself are deliberately spared from receiving an ablative level of heating, that is, the temperatures for these structures are less than 50 degrees C.
It should be recognized that the theory behind and practice of RF heat ablations has been known for decades, and a wide range of RF generators and electrodes for accomplishing such practice exist. For example, equipment for performing heat lesions is available from Radionics, Inc., located in Burlington, Massachusetts. Radio-frequency (RF) ablation is well known and described in medical and clinical literature. To that end, a research paper by E. R. Cosman, et al., entitled xe2x80x9cTheoretical Aspects of Radio-frequency Lesions in the Dorsal Root Entry Zone,xe2x80x9d Neurosurgery, vol. 15, no. 6, pp. 945-950 (1984), describing various techniques associated with radio-frequency lesions, is hereby incorporated by reference herein in its entirety. Also, a research paper by S. M. Goldberg, et al., entitled xe2x80x9cTissue Ablation with Radio-frequency: Effect of Probe Size, Gauge, Duration, and Temperature on Lesion Volume,xe2x80x9d Acad. Radiol., vol. 2, pp. 399-404 (1995), describes techniques and considerations relating to tissue ablation with radio-frequency energy, and is hereby incorporated by reference herein in its entirety.
According to the invention, a device for enlarging a urethral passage includes an elongate member having a distal portion configured for intraurethral placement in the urethral passage, and an electrode at the distal portion of the elongate member. The electrode is configured to be energized with high frequency energy to necrose tissue of the urethral wall and surrounding prostate tissue to form a cavity in the urethral passage. The electrode has an adjustable working length.
Embodiments of this aspect of the invention may have one or more of the following features.
A removable insulative member covers at least a portion of the electrode. The device includes an insulating sleeve and the electrode is movable relative to the insulating sleeve to adjust the working length. The electrode has a diameter greater than about 16 French to substantially occlude the urethra. The electrode is disposed on an outer surface of the distal portion of the elongate member. The device includes multiple electrodes at the distal portion of the elongate member, and multiple wires each for independently coupling one of the multiple electrodes to a high frequency electrical signal. The electrodes are spaced apart a distance of about 1 to 5 mm.
According to another aspect of the invention, a device for enlarging a urethral passage includes an elongate member having a distal portion configured for intraurethral placement in the urethral passage, and a plurality of electrodes at the distal portion of the elongate member. The electrodes are configured to be energized with high frequency energy to necrose tissue of the urethral wall and surrounding prostate tissue to form a cavity in the urethral passage. The electrodes are spaced apart a distance of about 1 to 5 mm to provide flexibility in the distal portion of the elongate member.
Embodiments of this aspect of the invention may include one or more of the following features.
The electrodes have a diameter greater than about 16 French to substantially occlude the urethra. The device includes multiple wires each for independently coupling one of the multiple electrodes to a high frequency electrical signal. The high frequency electrical signal can be selectively applied to each of the electrodes to adjust a length of the region of ablative heating. The electrodes are disposed on an outer surface of the distal portion of the elongate member. A removable insulative member covers at least a portion of one of the electrodes.
According to another aspect of the invention, a method of treating a urethral passage includes measuring a length of a patient""s prostate, and selecting a length of an electrode based on the measured length of the prostate. The electrode is configured to be energized with high frequency energy to necrose tissue of the urethral wall and surrounding prostate tissue to form a cavity in the urethral passage.
Embodiments of this aspect of the invention may include one or more of the following features.
The electrode includes multiple electrodes and the step of selecting includes determining which electrode to energize. The step of selecting includes removing insulation from the electrode. The step of selecting includes advancing an electrode relative to an insulating sleeve.
The method includes selecting a diameter of the electrode that substantially occludes the urethra, and energizing the electrode with high frequency energy to elevate the temperature of the urethra to at least 50xc2x0 C. to ablate tissue of a wall defining the urethral passage and ablate adjacent prostate tissue to form a cavity communicating with the urethral passage.
Advantages of the invention may include a minimally invasive ablation technique that simulates the advantages of TURP, for example, tailoring the formed cavity or void according to the length of the prostate and producing a cavity diameter that is beyond the superficial tissue layers around the urethra, that is cavity diameters greater than about 10 to 12 millimeters. An ablation volume within and around the prostatic urethra is created minimally invasively in accordance with the size of the patient""s prostate and other clinical criteria such as the preservation or non-preservation of the bladder neck, and matching the physiologic anatomy and size of the urethra and prostate for a specific patient.
The technique requires a very short time to perform, for example, less than ten minutes and preferably in the range of two to six minutes, in which time the patient can be maintained comfortably without undue anesthetic and without experiencing undue pain or distress. The procedure can be performed in a doctor""s office or in an outpatient setting, without requiring an operating room or extensive, sophisticated personnel such as anesthesiologists and nurses.
The ablation is performed for the treatment of BPH and the associated alleviation of urethral obstruction. The ablation can also be used to treat other diseases such as prostate cancer to alleviate urethral obstruction.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent form the description and drawings, and from the claims.